The present invention relates to a hex head wrench and in particular to a hex head wrench which has angled flank surfaces which progressively engage a fastener.
The hex head wrench is widely used with fasteners having a hexagonal opening in the head of the fastener. The commonly used wrench has six driving surfaces which engage the sides of the opening in the fastener and which imparts high stress on the corner portions of the wrench when torque is applied. In order to reduce this problem, U.S. Pat. No. 5,284,075 to Strauch et al disclose a screwing tool having flank sections which are convex in a circumferential direction and in which the central region of each flank has a non-convex intermediate section. Another approach to the problem is disclosed in U.S. Pat. No. 2,083,092 to Richer. A screw and a cooperating wrench have a series of alternating concave and convex arcs tangentially joining one another so as to form a plurality of equispaced inflections. Goss et al in U.S. Pat. No. 5,279,190 disclose a torque transmitting arrangement for a fastener drive system. The externally configured and the internally configured components are both provided with a series of mating, elliptically curved flutes and lobes.
The applicant is also aware of the following U.S. Patents which disclose tools for driving a fastener.
U.S. Pat. No. 3,658,105 Burt et al PA1 U.S. Pat. No. 4,269,246 Larson et al PA1 U.S. Pat. No. 4,338,835 Simons PA1 U.S. Pat. No. 4,625,598 Wolfram PA1 U.S. Pat. No. 5,259,279 Strauch
However, none of these patents disclose a wrench, and especially a hexagonal wrench, with a driving portion which has flank surfaces and radial surfaces to reduce stress and to transmit torque.